Why does the author say the relative figure is 'always larger than the absolute one when the baseline risk is low'?
A headline announces that eating a certain food raises the risk of a disease by fifty per cent. The figure sounds alarming, but on its own it tells us very little. If the disease affects two people in a thousand, a fifty per cent rise takes it to three in a thousand: one extra case for every thousand people. If it affects two in ten, the same rise means an extra one in ten. The relative change is the same; the absolute change is entirely different. Reports that give only the relative figure exaggerate small risks and are easy to produce, because the figure is always larger than the absolute one when the baseline risk is low. A responsible report gives both, and says who was studied.
Answer and explanation
Correct answer: E. A percentage change applies to a small starting number
- Step 1: With a low baseline, even a tiny absolute change is a large fraction of the baseline.
- Step 2: That is why the percentage looks dramatic.
Answer
A percentage change applies to a small starting number.
Why not the others: Units, journalists' additions, the food's effect and unstudied people are not mentioned.
Practise more Statistics and the news.
Free questions with an explanation for every one, and full timed LNAT mock tests.